N-193. Comparison of Cultivable Purple Non-Sulfur Anoxyphototrophs from Tropical Hypersaline Microbial Mats at Cabo Rojo Salterns of Puerto Rico during Seasonal Changes

K. M. Soto-Feliciano¹, L. F. Hernández-Cabassa¹, P. Sahai¹, K. Y. Flores-Burgos¹, L. Casillas-Martínez², C. Ríos-Velázquez¹;
¹Univ. of Puerto Rico, Mayaguez, PUERTO RICO, ²Univ. of Puerto Rico, Humacao, PUERTO RICO.

The purple non-sulfur anoxyphototrophs (PNSA) community structure of naturally occurring microbial mats in the Cabo Rojo Salterns was studied by conventional cultivation methods and molecular techniques. Microorganisms at the location are exposed to oxygen and sulfur variations as well as seasonal changes, such as pluvial precipitation. This research focuses on comparing isolated and characterized cultivable PNSA present in young and mature mats from two different sites of the Cabo Rojo Salterns, during rainy and dry seasons. Microbial mats were dissected and the three layers were cultivated in solid and liquid media. After being incubated anaerobically in the presence of light, a characteristic reddish bloom was observed, and pigmented individual colonies were isolated by streaking the bloomed samples on selective media. The putative PNSA isolates were characterized microscopically, biochemically and molecularly. A total of 10 PNSA candidates were isolated from the rainy season; 6 and 4 from the mature and young mat, respectively. During the dry season, 9 PNSA were isolated; 4 and 5 from mature and young mats, respectively. All the isolates were gram-negative straight and spiral rods of variable sizes. Globally, three morphotypes were identified. Morphotype 1 contains two variants, where one of them is present only during the rainy season in both mats. In contrast, morphotype 2 is present in both mats during both seasons. Finally, morphotype 3 contains two variants, one of them absent in the rainy season of the mature mat, and the other one absent in the rainy season of the young mat. Biochemical and molecular analysis revealed the presence of characteristic bacteriochlorophyl peaks (800 and 850nm). The presence of a photosynthetic apparatus was also confirmed molecularly by amplifying and sequencing the pufM gene. Sequencing of 16S rDNA and further in silico analysis suggests the presence of the genus Rhodospirillum, as well as various unidentified members of the Rhodospirillaceae family, including several unidentified APB similar to Vibrio sp. These results suggest microbial mat-specific as well as season-specific morphotypes.